1. Field of the Invention
The present invention relates to a suction device, and in particular to a stepwise powerful suction device that is controlled to selectively generate suction forces of different magnitudes for different applications in holding panels or boards of different thicknesses.
2. The Related Arts
FIGS. 1 and 2 of the attached drawings illustrate a conventional suction device, which comprises two suction holders 11, two suction elements 12, two springs 13, two switch levers 14 and a support frame 15. A portion of the support frame 15 forms a handle. Each suction holder 11 forms a central hole 112 and has a top forming a platform 111. The suction element 12 is made of a deformable material and forms an upright post 122. The upright post 122 forms at an upper end section thereof a pin hole 123 that receives therein a pin 124. Each switch lever 14 has an end forming a pivoting portion 141 in which a pivot hole 143 is defined. The pivoting portion 141 also has a camming edge 142. The spring 13 encompasses the upright post 122 of the suction element 12. The upright post 122 of the suction element 12 extends through the hole 112 of the suction holder to position the suction element 12 under the bottom of the suction holder 11 with the spring 13 normally biasing the suction element 12 away from the bottom of the suction holder 11. The upright post 122 is set to have the pin hole 123 thereof aligned with pivot hole 143 of the switch lever 14 to allow the pin 124 to extend through both, whereby the switch lever 14 is rotatable with respect to the suction holder 11. In operation, the rotatable and thus position-changeable switch lever 14 is arranged to have the camming edge 142 thereof engaging the platform 111 of the suction holder 11 so that rotation of the switch lever 14 causes, via the pivotal joint thereof with the upright post 122, the suction element 12 to be forced upward. With the suction element 12 positioned on a smooth surface of for example a glass panel or a board or the likes, vacuum is induced inside the suction element 12 thereby generating a suction force to hold the glass panel or the board to the suction element 12.
The conventional suction device has disadvantages. For example, the suction force so induced by the suction element is not adjustable so that it only provides a constant magnitude. This works for holding thick glass panels or thick boards that are capable to endure a large force without breaking or fracture, but when applied to a glass panel or a board of a small thickness, which is capable to sustain a large force, the fixed magnitude suction force generated by the conventional suction device may unexpectedly break the glass panel or board, leading to property loss or even damage to people.
In view of the above discussed drawbacks, it is desired to have a suction device that overcomes the above problems.